Ladders are commonly used for a variety of applications and are of two general types. One type is a folding ladder, commonly called a step ladder, which is self supporting. Step ladders are typically used for such tasks as pruning, painting ceilings, or other similar tasks where it may be impossible to lean the ladder against a structure for support. The other type of ladder which is well known is the straight extension ladder. This type of ladder is simply leaned against the wall or some other structure when standing or climbing on the ladder.
Ladders which are constructed so that they may be used as both step ladders and as straight extension ladders have long been known in the art. Typically, such ladders are constructed with hinges in the middle of the side rails. The hinges permit the ladder to be folded into a step ladder configuration or unfolded into a straight extension ladder configuration. Such ladders, commonly referred to as combination step and extension ladders, are very versatile and they combine the desirable features of both types of ladders.
Further improvements on such step ladders include foldable ladders or ladders which are adjustable to a variety of positions so that they can be used as scaffolding or for other support configurations. Such foldable or adjustable ladders include two or more adjustable locking hinges which enable the ladder to conform to the desired positions. A wide variety of adjustable locking hinges are known in the prior art.
The applicant has now developed a novel and improved hinge mechanism for use in such adjustable ladders, as will be detailed in the following description.